Rotary switch, with vibration resistant resilient displaceable fixed contact structure



Sept. 6, 1966 BUTLER 3,271,533

ROTARY SWITCH WITH RATION RESISTANT RESILIENT DISPLACEABLE F D CONTACTSTRUCTURE Filed 28, 1963 FIG. 4

FIG. 7

INVENTOR. MAURICE C. BUTLER Q JM A, p32 Ww, Ak

[MY 1T- ATTORNEYS United States Patent v 3,271,533 ROTARY SWITCH, WITHVIBRATION RESISTANT RESILIENT DISPLACEABLE FIXED CONTACT STRUCTUREMaurice C. Butler, San Diego, Calif., assignor to Kinetics Corporation,Solana Beach, Calif., a corporation of California Filed Oct. 28, 1963,Ser. No. 319,107 6 Claims. (Cl. 200-9) The present invention relates toa rotary electrical switch which is vibration resistant, has a longlife, functions well in a dry state, passes a high electrical currentand has characteristics which make it desirable for use in circuitswhich have inductive loads.

The switch of the present invention is comprised of moving andstationary contacts which contacts are arranged and formed in such a wayas to give the abovedescribed characteristics.

The moving contacts rotate about an axis. As the moving contacts rotate,their outer tips define a circle. Each moving contact cooperates withone or more corresponding fixed contacts which are substantially tangentto the circle defined by the moving contact. However, the shortestdistnace from the axis to the fixed contacts is less than the radius ofthe circle. Ordinarily, such a condition would prohibit the rotation ofthe moving contact. However, the fixed contacts are resilientlydisplaceable in a direction radial of the axis.

When a fixed contact is resiliently displaced by a moving contact, aforce is developed between the moving and fixed contacts. The highcontact pressure thus developed between the contacting surfaces reducesthe electrical contact resistance, and therefore permits the passage ofhigh electrical currents.

Electrical contact resistance which reduces the current carryingcapacity of the switch, is increased by the formation of films, ofcompounds (e.g., oxides), and by the presence of extraneous matter.These films, compounds, and extraneous matter collections arecontinually removed by the wiping action of the contacting surface ofthe moving contact sliding over its corresponding fixed contacts. Thiswiping action therefore helps to maintain a low contact resistance andthus permits the passage of high electrical currents.

Since the high contact force and the wiping action maintain a lowelectrical contact resistance, high switch temperatures are notproduced. Therefore, since cooling liquids are not required, the switchmay be operated in a dry state.

The switch of the present invention is very resistant to vibration. Thisresistance is due to three characteristics of the switch: The highcontact force, the natural vibrational frequency of the contacts, andthe positive contacting mechanism.

As previously discussed, the high contact pressure between the movingand stationary contacts is produced by resilient displacement of thesubstantially fixed contact.

By making the contacts such that their natural vibrational frequenciesare substantially different than the frequency of rotation of themovable contacts, the contacts do not resonate.

To avoid arc erosion of switches used in circuits having inductiveloads, the contacting portions of the switches must separate at a highrelative velocity. When used in conjunction with a Geneva drive systemthe contacts of this switch have a high make and break velocity. TheGeneva drive system rotates at a non-uniform rate. The Geneva systemcould be so adjusted as to give the switch contacts a high relativevelocity during the making and breaking of contact, and zero relativevelocity during period when the contacts are in contact.

3,271,533 Patented Sept. 6, 1966 Other features and advantages of thepresent invention will be apparent from the following description,reference being made to the accompanying drawing wherein preferredembodiments of the invention are illustrated.

In the drawing:

FIG. 1 is a perspective view of the moving contacts of one embodiment ofthe invention;

FIG. 2 is a cross-sectional view of the embodiment of the inventionwhich uses the moving contacts shown in.

FIG. 1;

FIG. 3 is a fragmentary view of another embodiment of the contacts shownin FIG. 2, drawn at a larger scale;

FIG. 4 is a plan view of FIG. 3 taken along line 4-4 of FIG. 3;

FIG. 5 is a perspective view of the moving contacts of anotherembodiment of the invention;

FIG. 6 is a cross-sectional view of the embodiment of the inventionwhich uses the moving contacts shown in FIG. 5; and

FIG. 7 is a fragmentary view of the contacts shown in FIG. 5, drawn at alarger scale.

Referring in detail to the drawing, FIGS. 1, 2 and 3 illustrate oneembodiment of the invention. FIG. 1 shows the moving portion of theswitch. The moving electrical contacts 20 are held by the shaft 22. Theshaft may be either an electrical conductor or non-conductor, however,if made of a conductor, the moving contacts 20 must be insulated fromthe shaft 22.

FIG. 2 shows a cross-sectional view of the moving contacts 20 and theshaft 22 positioned within the switch. Two of the resilientlydisplaceable substantially fixed contacts 26 are shown held in positionby support means herein shown as the switch casing 28. The casing may bemade of either an electrical conductor or non-conductor, however, ifrnade of a conductor, the fixed contacts 26 must be insulated from thecasing 28. Both ends of contacts 26 may be fixed to the casing, or oneend may be fixed and the other end slidable relative to the casing. Inthe first case, both ends fixed, the resilient displacement of thecontact requires a greater force than the second case of one end fixedand one end free. I

The shaft 22 is held in place by bearings 24, which are mounted in theends of the switch casing 28.

In FIG. 2 each of the fixed contacts 26, which are straight when not incontact with the moving contacts 20, is shown resiliently displaced bythe moving contacts 20. This resilient displacement produces a highcontact pressure between the cont-acts.

FIGS. 1 and 2 show moving contacts 20 which are continuous through theshaft 22. Thus one of the moving contacts combined with two of thestationary contacts comprises one switching circuit. While thisconstruction is used to disclose the invention, other constructions areobvious. For example, the moving contacts could be discontinuous throughthe shaft. Then any one of the moving contacts 20 could be electricallyinterconnected to one or more of the other moving contacts 20. Inaddition the moving contacts 20 could be disposed at various locationson the shaft, each of these moving contacts 20 having one or more fixedcontacts, variously disposed, with which to contact as it rotates on theshaft. This switch can therefore perform a complex switching sequencebecause of the variety of arrangements of the fixed and moving contactsand the variety of ways of electrically interconnecting the contacts.

The embodiment of FIGS. 1 and 2 has the moving contacts 20 disposed intwo planes which are at right angles to one another. Therefore, themoving contacts in one plane break contact before the contacts in theother plane make contact. In this embodiment the circuit is broken attwo places simultaneously. This double break characteristic reduces arcerosion, since the total are voltage drop is divided into two smallervoltage drops. The total are voltage drop of a conventional switch,single break, is made to occur at one place.

FIG. 3 is an expanded view of another embodiment of the contacts 20 and26. This embodiment utilizes 'bi-metallic contacts 20 and 26. Theleading and trailing portions of the contacts which are first and lastto make contact, 30 and 32, are made of a material that is resistant toelectric arc erosion, such as tungsten. Whereas the remaining portionsof the contacts are made of a material which has a low electricalresistivity, such as copper.

FIG. 4 is a top view of the =bi-metallic fixed contact 26. The fixedcontact width is greater than the width of the inserts 32 so as toprovide a low electrical resistance path around the inserts 32.

FIGS. 5, 6 and 7 show another embodiment of the invention which usescam-like moving contacts 34.

In FIG. S'the cam-like moving contacts 34 are disposed along the shaft36. The moving contacts are insulated from the shaft and may or may notbe insulated from one another.

FIG. 6 shows a cross-sectional view of the shaft 36, and one of thecam-like moving contacts 34 positioned within the switch. Two of theresiliently displaceable substantially fixed contacts 40 are shown heldin position by the switch casing 42.

In FIG. 6 each of the fixed contacts 40 are shown resiliently displacedby one of the cam-like moving contacts, said displacement producing acontact pressure between the contacts.

The shaft 36 is held in place by bearings 38 mounted on the end of theswitch casing 42.

The cam-like moving contact 34 includes a contacting surface 44 whichhas a constant radius of curvature with respect to the longitudinal axisof the switch. When the shaft 36 revolves at a uniform rate, the closecircuit time for any one cam-like contact is dependent upon thecircumferential length of the contact surface 44.

By selective electrical interconnection of cam-like contacts 34, byvarying the circumferential lengths of the contacting surfaces 44, byvarying the angular location of the contacting surfaces 44 relative tothe longitudinal axis of the shaft 36, and by varying the rotationalspeed of the shaft, a great variety of complex switching operations canbe accomplished by the switch. The switchs versatility is furtherenhanced 'by the fact that the relative position of the fixed contactsfor anyone cam-like contact 34, may be varied.

FIG. 7 shows an arc erosion prevention construction similar to the oneshown in FIG. 3. Inserts 46 and 47 are made of an electrical conductorwhich is resistant to are erosion, whereas, the remaining portions ofcontacts 34 and 40 are made of a material having a low electricalresistivity such as copper.

By proper positioning of the contact surfaces 44, it is possible,assuming the necessary electrical interconnections are made, for one ofthe switches in a circuit to close before another one opens. This makebefore break feature reduces are erosion because before a switch breaksits load is partially transferred to another switch.

It is apparent from the above description that I have invented aversatile rotary electrical switch which is vibration resistant, has along life, functions well in a dry state, passes a high current, andfunctions well in circuits with inductive loads.

While the forms of embodiment herein shown and described constitutepreferred forms, it is understood that other forms may be adoptedfalling within the scope of the laims .that follow.

- 1. A rotatable electrical switch, comprising in combination:

( a rotatable element;

(B) a conductor carried by and extending radially of the axis of theelement, said conductor having:

(l) a section having highly conductive characteristics;

(2) a leading section having relatively high resistance to electric arccharacteristics;

(C) a yielding contact;

(D) and means for rotatably supporting the rotatable element and forfixedly supporting the yielding contact under tension constantly andspaced from said element and in a position to be engaged first by saidleading section and thereafter by the first mentioned section of theconductor upon rotation of said element.

2. A rotatable electrical switch, comprising in combination:

(A) a rotatable element;

(B) a conductor carried by and extending radially of the axis of theelement, said conductor having:

(1) a section having high conductive characteristics;

(2) a trailing section having relatively high resistance to electric arccharacteristics;

(C) a yielding contact;

(D) and means for rotatably supporting the rotatable element and forfixedly supporting the yielding contact under tension constantly andspaced from said element and in a position to be engaged by said firstmentioned section of the onductor, then by the trailing edge andthereafter to be disengaged from the trailing edge upon rotation of saidelement.

3. A rotatable electrical switch comprising in combination:

(A) a rotatable element;

(B) a conductor carried by and extending radially of the axis of theelement, said conductor having:

(1) a section having high conductive characteristics;

(2) a leading section having relatively high resistance to electric arccharacteristics;

(3) a trailing section having relatively high resistance to electric arccharacteristics;

(C) a yielding contact;

(D) and means for rotatably supporting the rotatable element and forfixedly supporting the yielding contact under tension constantly andspaced from said element and in a position to be engaged sequentially bysaid leading section, then by the first mentioned section of theconductor, then by the trailing section and thereafter to be disengagedfrom the trailing edge upon rotation of said element.

4. A rotatable electrical switch comprising in combination:

(A) a rotatable element;

(B) a conductor carried by and extending radially of the axis of theelement;

(C) a yielding contact, said contact having:

(1) a section having high conductive characteristics;

(2) a section, included in the surface of the first mentioned section,having relatively high resistance to electric arc characteristics;

(D) and means for rotatably supporting the rotatable element and forfixedly supporting the yielding contact under tension constantly andspaced from said element and in a position that the conductor engagesthe second mentioned section and thereafter the first mentioned sectionupon rotation of said element.

5. A rotatable electrical switch comprising in combination:

(A) a rotatable element;

(B) a conductor carried by and extending radially of the axis of theelement;

(C) a yielding contact, said contact having:

(1) a section having high conductive characteristics;

(2) a section, included in the surface of the first mentioned section,having relatively high resistance to electric arc characteristics;

(D) and means for rotatablysupporting the rotatable element and forfixedly supporting the yielding contact under tension constantly andspaced from said element and in a position that the conductor engagesthe first mentioned section and thereafter the second mentioned sectionupon rotation of said element.

6. A rotatable electrical switch comprising in combination:

(A) a rotatable element;

(B) a conductor carried by and extending radially of the axis of theelement;

(C) a yielding contact, said contact having:

(1) a section having high conductive characteristi-cs;

(2) a section, included in the surface of the first mentioned section,having relatively high resistance to electric arc characteristics;

(3) a second section, included in the surface of the first mentionedsection, having characteristics which render it highly resistant toelectric arcing;

(D) and means for rotatably supporting the rotatable element and forfixedly supporting the yielding contact under tension constantly andspaced from said element and in a position that the conductorsequentially engages the second mentioned section, the first mentionedsection, the third mentioned section and thereafter disengages thecontact from the third mentioned section upon rotation of said element.

References Cited by the Examiner UNITED STATES PATENTS 1,994,821 3/1935Hunter 200-9 X 2,006,959 7/ 1935 Mack.

2,501,164 3/1950 Durst 200166 2,501,456 3/1950 Thias et a1.

2,503,888 4/1950 Schultz 200-8 X 2,518,030 8/1950 Kuperus 200-166 X2,814,009 11/1957 Emley et al 200-8 X 3,019,323 1/ 196 2 Daniels 200155ROBERT K. SCHAEFER, Primary Examiner.

KATHLEEN H. CLAFFY, ROBERT S. MACON,

Examiners.

J. R. SCOTT, Assistant Examiner.

1. A ROTATABLE ELECTRICAL SWITCH, COMPRISING IN COMBINATION: (A) AROTATABLE ELEMENT: (B) A CONDUCTOR CARRIED BY AND EXTENDING RADIALLY OFTHE AXIS OF THE ELEMENT, SAID CONDUCTOR HAVING: (1) A SECTION HAVINGHIGHLY CONDUCTIVE CHARACTERISTICS; (2) A LEADING SECTION HAVINGRELATIVELY HIGH RESISTANCE TO ELECTRIC ARC CHARACTERISTICS; (C) AYIELDING CONTACT; (D) AND MEANS FOR ROTATABLY SUPPORTING THE ROTATABLEELEMENT AND FOR FIXEDLY SUPPORTING THE YIELDING CONTACT UNDER TENSIONCONSTANTLY AND SPACED FROM SAID